1st thing i would do is locate a local pharmacy, such a Rite-Aid or savon or cvs so forth, and try to look online to see if your local drug store offers the morning after pill. go to the pharmacy and talk to one of the pharmacist, tell them your situation and ask them to prescrible the pill to you. It'll cost around 30-60 bucks i believe. There has to be a pharmacist there inorder to prescrible u the medicine.
If you want to do this without ur mom knowing, i guess you can just tell her that u need to walk to the drugs store really fast to get some pain-relievers or something.
Correct me if i'm wrong about getting the morning after pill, cause i know that you can obstain it from a local pharmacy.
I hope everything works out.